The great artery is the aorta.The thickest artery tube in the human body is the main conduit for transporting blood to all parts of the body.Near cardiacaortaThe pulmonary artery is called the great artery.Its tube wall is mainly composed of elastic fibers, so it is also called elastic artery.
As the great arteries contain a large number of elastic fibers, they can cushion the impact of cardiac blood flow when the heart contracts;When the heart relaxes, it can maintain the balance of blood flow velocity.The great arteries, especially the aorta, are prone to atherosclerosis;Inflammatory lesions may also occur in the great arteries.
2. Arteries:
All blood vessels and their branches from the ventricles are called arteries.It is a blood vessel that transports blood from the ventricle to organs and tissues of the whole body.The arteries and their branches from the left ventricle transport oxygen saturated arterial blood, while the arteries and their branches from the right ventricle transport venous blood.
According to the size of artery diameter, it can be divided into four grades: large, medium, small and micro.There is no obvious boundary between them.Its common basic structure is composed of three layers of inner, middle and outer membranes.
The major arteries generally refer to the aorta, pulmonary artery, innominate artery, common carotid artery, subclavian artery, common iliac artery and femoral artery.This kind of artery has the thickest tunica media, which is mainly composed of elastic membrane formed by a large number of elastic fibers (about 40-70 layers in adults) and circular smooth muscle.Therefore, the elasticity of the tube wall is large, so it is also called elastic artery.It can not only cushion the strong pressure generated when the heart is contracting, but also promote the directional flow of blood by its elastic retraction when the heart is relaxing.
Except for the great arteries, all arteries with a diameter of more than 1 mm belong to the middle arteries.Its structural feature is the thick middle layer of the tube wall, which is mainly composed of a large number of circular smooth muscles (about 10~40 layers for adults) and a small amount of elastic fibers and collagen fibers.Therefore, the contractility of the tube wall is large, so it is also called muscular artery.It can regulate the blood supply of local organs.
Small arteries generally refer to those with a diameter of less than 1 mm and more than 300 microns.The tube wall structure is basically similar to that of the middle artery, but gradually becomes thinner.The membrane is only composed of 1-4 layers of smooth muscle, so it is also a muscular artery, and also has the function of regulating the blood flow in organs and tissues.Generally, arterioles with diameters below 300 microns are called arterioles.It eventually migrates into capillaries.
Arteries can change with age.In addition to normal development, these changes can also occur degenerative, even pathological changes.Strengthening physical exercise can enhance the functional activities of arteries to prevent or delay their degenerative or pathological changes.
Morphological structure of great arteries
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The great arteries are the first to third grade arteries from the heart.The diameter of the great arteries is large and round.The membrane contains a lot of elastic tissue, also called elastic artery.The human aorta, pulmonary artery, brachiocephalic trunk, subclavian artery and common carotid artery are all great arteries.The intima of the great arteries is divided into three layers: the endothelium is composed of polygonal single-layer flat cells, the cytoplasm is not obvious, and most of the nuclei are spindle shaped;The subendothelial layer consists of fine glial fibers and amorphous matrix, as well as elastic fibers, fibroblasts and migratory cells;The internal elastic membrane is composed of multi-layer perforated elastic membrane, also known as window membrane. There is a small amount of connective tissue and sometimes a small amount of smooth muscle in the space between the membranes.In recent years, it is believed that the intimal cells of the great arteries can secrete some microcirculatory hormones to participate in the regulation of local microcirculation;The middle membrane is the thickest of the three membranes, and its main component is the window membrane formed by elastic tissue.In human aorta, there are about 50~60 layers around the tube wall, and branches are connected with each other.The space between membranes is wide, with a layer of circular smooth muscle and a little connective tissue.The main components of the matrix in the middle membrane are sulfur-containing mucoprotein polysaccharides, which are the components of the middle membrane that have contractibility under normal conditions.However, under pathological conditions, the matrix can form cartilage or calcification to form bone. At this time, the arterial wall loses its elasticity and contractility, resulting in arteriosclerosis.The outer membrane is relatively thin, and the outer layer is a longitudinal glial fiber. There is an external elastic membrane at the junction with the middle membrane, and there is no obvious boundary between it and the middle membrane.There are also vascular trophoblastic tubes and nerves in the adventitia.The structure and function of the great arteries are closely related.Because it contains a large amount of elastic tissue, the expansion of the tube wall significantly increases the diameter of the tube, which can accommodate the blood from the heart when the heart is contracting, and buffer the pressure of the heart beat. When the heart is relaxing, the elastic tissue of the great artery returns and the smooth muscle contracts, so that the blood in it continues to flow to the far end of the artery without interruption, and maintains the effective blood perfusion of the tissue.The outer membrane of the great artery can prevent the elastic tissue in the middle membrane from overstretching, thus keeping the blood pressure in the great artery up and down to a certain extent.When the outer membrane is damaged, the middle membrane may protrude due to the pressure inside the tube, and in serious cases, an aneurysm may form.
